Sensor device

Abstract

A sensor device ( 4 ) detects a state of a lubricant. The sensor device ( 4 ) has a sensor unit ( 6 ). The sensor unit ( 6 ) is designed to measure the impedance of the lubricant according to the frequency of an applied alternating current. The sensor device ( 4 ) has an evaluation unit ( 8 ) which is designed to determine a state of the lubricant based on the measured impedance.

What is claimed is: 
     
         1 . A sensor device for detecting a state of a lubricant, the sensor device comprising:
 a sensor unit configured to measure the impedance of the lubricant according to the frequency of an applied alternating current;   an evaluation unit configured to determine a state of the lubricant based on the measured impedance.   
     
     
         2 . The sensor device according to  claim 1 , wherein the sensor unit has a housing having a supply opening and a discharge opening for supplying and discharging lubricant to the housing and from the housing. 
     
     
         3 . The sensor device according to  claim 1 , wherein the sensor unit has at least two electrodes arranged to contact with the lubricant. 
     
     
         4 . The sensor device according to  claim 3 , wherein the sensor unit has an alternating current source, which is connected to the electrodes in order to apply alternating current to the electrodes. 
     
     
         5 . The sensor device according to  claim 1 , wherein the evaluation unit is configured to compare the measured impedance with a reference value. 
     
     
         6 . The sensor device according to  claim 5 , wherein the sensor unit is configured to measure the impedance of the lubricant in an initial state of the lubricant, and to store this as a reference value. 
     
     
         7 . The sensor device according to  claim 1 , wherein the sensor device has a temperature-control unit, and wherein the temperature-control unit is designed to regulate the temperature of the lubricant, at least in the sensor unit, to a predetermined temperature. 
     
     
         8 . The sensor device according to  claim 7 , wherein the evaluation unit is designed to compare the measured impedance with a reference value, wherein the reference value corresponds to the impedance of a reference lubricant at the predetermined temperature. 
     
     
         9 . The sensor device according to  claim 1 , wherein the sensor device has a temperature sensor, which is designed to measure a temperature of the lubricant, and wherein the evaluation unit is designed to determine the state of the lubricant based on the measured impedance and the measured temperature. 
     
     
         10 . The sensor device according to  claim 1 , wherein the sensor device is part of a lubrication system, in particular a central lubrication system, or wherein the sensor device is arranged separately from a lubrication system in a laboratory environment. 
     
     
         11 . The sensor device according to  claim 2 , wherein the sensor unit has at least two electrodes arranged to contact with the lubricant. 
     
     
         12 . The sensor device according to  claim 11 , wherein the sensor unit has an alternating current source, which is connected to the electrodes in order to apply alternating current to the electrodes. 
     
     
         13 . The sensor device according to  claim 12 , wherein the evaluation unit is configured to compare the measured impedance with a reference value. 
     
     
         14 . The sensor device according to  claim 13 , wherein the sensor unit is configured to measure the impedance of the lubricant in an initial state of the lubricant, and to store this as a reference value. 
     
     
         15 . The sensor device according to  claim 14 , wherein the sensor device has a temperature-control unit, and wherein the temperature-control unit is designed to regulate the temperature of the lubricant, at least in the sensor unit, to a predetermined temperature. 
     
     
         16 . The sensor device according to  claim 15 , wherein the evaluation unit is designed to compare the measured impedance with a reference value, wherein the reference value corresponds to the impedance of a reference lubricant at the predetermined temperature. 
     
     
         17 . The sensor device according to  claim 16 , wherein the sensor device has a temperature sensor, which is designed to measure a temperature of the lubricant, and wherein the evaluation unit is designed to determine the state of the lubricant based on the measured impedance and the measured temperature. 
     
     
         18 . The sensor device according to  claim 17 , wherein the sensor device is part of a lubrication system, in particular a central lubrication system, or wherein the sensor device is arranged separately from a lubrication system in a laboratory environment. 
     
     
         19 . A lubrication system comprising:
 at least one lubrication point;   a lubricant tank;   a pump configured to deliver lubricant from the lubricant tank to the at least one lubrication point;   one or more lubricant-conducting lines connecting the lubricant tank, the pump and the at least one lubrication point;   a sensor device according to  claim 1 , the sensor device being arranged in one or more of the lubricant-conducting lines, in the pump, in a lubricant collection tank, and/or at the at least one lubrication point.   
     
     
         20 . A method for detecting a state of a lubricant comprising:
 measuring the impedance of the lubricant according to the frequency of an applied alternating current; and   determining a state of the lubricant based on the measured impedance.